Targeted silencing of elongation factor 2 kinase suppresses growth and sensitizes tumors to Doxorubicin in an orthotopic model of breast cancer

Eukaryotic elongation factor 2 kinase (eEF-2K), through its phosphorylation of elongation factor 2 (eEF2), provides a mechanism by which cells can control the rate of the elongation phase of protein synthesis. The activity of eEF-2K is increased in rapidly proliferating malignant cells, is inhibited during mitosis, and may contribute to the promotion of autophagy in response to anti-cancer therapies. The purpose of this study was to examine the therapeutic potential of targeting eEF-2K in breast cancer tumors. Through the systemic administration of liposomal eEF-2K siRNA (twice a week, i.v. 150 μg/kg), the expression of eEF-2K was down-regulated in vivo in an orthotopic xenograft mouse model of a highly aggressive triple negative MDA-MB-231 tumor. This targeting resulted in a substantial decrease in eEF2 phosphorylation in the tumors, and led to the inhibition of tumor growth, the induction of apoptosis and the sensitization of tumors to the chemotherapy agent doxorubicin. eEF-2K down-modulation in vitro resulted in a decrease in the expression of c-Myc and cyclin D1 with a concomitant increase in the expression of p27(Kip1). A decrease in the basal activity of c-Src (phospho-Tyr-416), focal adhesion kinase (phospho-Tyr-397), and Akt (phospho-Ser-473) was also detected following eEF-2K down-regulation in MDA-MB-231 cells, as determined by Western blotting. Where tested, similar results were seen in ER-positive MCF-7 cells. These effects were also accompanied by a decrease in the observed invasive phenotype of the MDA-MB-231 cells. These data support the notion that the disruption of eEF-2K expression in breast cancer cells results in the down-regulation of signaling pathways affecting growth, survival and resistance and has potential as a therapeutic approach for the treatment of breast cancer.     

Reprogramming of non-genomic estrogen signaling by the stemness factor SOX2 enhances the tumor-initiating capacity of breast cancer cells

The restoration of pluripotency circuits by the reactivation of endogenous stemness factors, such as SOX2, may provide a new paradigm in cancer development. The tumoral stem cell reprogramming hypothesis, i.e., the ability of stemness factors to redirect normal and differentiated tumor cells toward a less-differentiated and stem-like state, adds new layers of complexity to cancer biology, because the effects of such reprogramming may remain dormant until engaged later in response to (epi)genetic and/or (micro)environmental events. To test this hypothesis, we utilized an in vitro model of a SOX2-overexpressing cancer stem cell (CSC)-like cellular state that was recently developed in our laboratory by employing Yamanaka’s nuclear reprogramming technology in the estrogen receptor α (ERα)-positive MCF-7 breast cancer cell line. Despite the acquisition of distinct molecular features that were compatible with a breast CSC-like cellular state, such as strong aldehyde dehydrogenase activity, as detected by ALDEFLUOR, and overexpression of the SSEA-4 and CD44 breast CSC markers, the tumor growth-initiating ability of SOX2-overexpressing CSC-like MCF-7 cells solely occurred in female nude mice supplemented with estradiol when compared with MCF-7 parental cells. Ser118 phosphorylation of estrogen receptor α (ERα), which is a pivotal integrator of the genomic and nongenomic E₂/ERα signaling pathways, drastically accumulated in nuclear speckles in the interphase nuclei of SOX2-driven CSC-like cell populations. Moreover, SOX2-positive CSC-like cells accumulated significantly higher numbers of actively dividing cells, and the highest levels of phospho-Ser118-ERα occurred when chromosomes lined up on a metaphase plate. The previously unrecognized link between E₂/ERα signaling and SOX2-driven stem cell circuitry may significantly impact our current understanding of breast cancer initiation and progression, i.e., SOX2 can promote non-genomic E₂ signaling that leads to nuclear phospho-Ser118-ERα, which ultimately exacerbates genomic ER signaling in response to E₂. Because E₂ stimulation has been recently shown to enhance breast tumor-initiating cell survival by downregulating miR-140, which targets SOX2, the establishment of a bidirectional cross-talk interaction between the stem cell self-renewal regulator, SOX2, and the local and systemic ability of E₂ to increase breast CSC activity may have profound implications for the development of new CSC-directed strategies for breast cancer prevention and therapy.     

The effects of shRNA-mediated gene silencing of transcription factor SNAI1 on the biological phenotypes of breast cancer cell line MCF-7

Developing spermatozoa require a series of posttesticular modifications within the luminal environment of the epididymis to achieve maturation; this involves several surface modifications including changes in plasma membrane lipids, proteins, carbohydrates, and alterations in the outer acrosomal membrane. Epididymal maturation can therefore allow sperm to gain forward motility and fertilization capabilities. The objective of this study was to identify maturation-dependent protein(s) and to investigate their role with the production of functionally competent spermatozoa. Lectin blot analyses of caput and cauda sperm plasma membrane fractions identified a 17.5 kDa wheat germ agglutinin (WGA)-binding polypeptide present in the cauda sperm plasma membrane not in the caput sperm plasma membrane. Among the several WGA-stained bands, the presence of a 17.5 kDa WGA-binding polypeptide band was detected only in cauda epididymal fluid not in caput epididymal fluid suggesting that the 17.5 kDa WGA-binding polypeptide is secreted from the cauda epididymis and binds to the cauda sperm plasma membrane during epididymal transit. Proteomic identification of the 17.5 kDa polypeptide yielded 13 peptides that matched the sequence of peroxiredoxin-5 (PRDX5) protein (Bos Taurus). We propose that bovine cauda sperm PRDX5 acts as an antioxidant enzyme in the epididymal environment, which is crucial in protecting the viable sperm population against the damage caused by endogeneous or exogeneous peroxide.     

The oncogenic transcription factor FOXM1 and anticancer therapy

Comment on: Halasi M,et al. PLoS One 2012; 7:e31761.     

人巨细胞病毒感染与乳腺癌关系的研究进展

人巨细胞病毒(human cytomegalovirus,HCMV)是β疱疹病毒家族成员,全世界70%以上人口感染过该病毒。HCMV通常以潜伏感染形式存在于宿主体内,并产生了逃避宿主免疫系统识别和清除等多种能力,可通过表达HCMV基因及蛋白发挥肿瘤调节作用,干扰细胞代谢过程,促进肿瘤的发生和发展。乳腺癌是女性最常见的恶性肿瘤之一,而HCMV在非肿瘤和乳腺癌患者乳腺上皮细胞中的阳性检出率较高,同时有研究表明晚期暴露于HCMV可引起乳腺癌。近期新型抗HCMV药物对乳腺癌靶向治疗的临床有效性也再次提示,HCMV可能与乳腺癌的发生和发展密切相关。本文主要综述了HCMV的致癌潜能及其与乳腺癌发生和发展的潜在关联。     

Expression of the murine transcription factor SOX3 during embryonic and adult neurogenesis

Previous studies have shown that Sox3 is expressed in nascent neuroprogenitor cells and is functionally required in mammals for development of the dorsal telencephalon and hypothalamus. However, Sox3 expression during embryonic and adult neurogenesis has not been examined in detail. Using a SOX3-specific antibody, we show that murine SOX3 expression is maintained throughout telencephalic neurogenesis and is restricted to progenitor cells with neuroepithelial and radial glial morphologies. We also demonstrate that SOX3 is expressed within the adult neurogenic regions and is coexpressed extensively with the neural stem cell marker SOX2 indicating that it is a lifelong marker of neuroprogenitor cells. In contrast to the telencephalon, Sox3 expression within the developing hypothalamus is upregulated in developing neurons and is maintained in a subset of differentiated hypothalamic cells through to adulthood. Together, these data show that Sox3 regulation is region-specific, consistent with it playing distinct biological roles in the dorsal telencephalon and hypothalamus.     

Epigenetic gene silencing in the Wnt pathway in breast cancer

Breast cancer is one of the most common malignancies in women. Despite advances in treatment of endocrine-dependent tumors, the complete molecular basis of transformation is still unknown. What is clear is that a variety of genetic lesions and epigenetic modifications are present in the neoplasm. Disregulation of several signaling pathways is known to be associated with breast cancer development, among them is the wingless and integration site growth factor (Wnt) pathway. While genetic mutations of certain components of this pathway, such as APC, are significant contributing factors for colorectal cancers, they are typically not the predominate mechanism associated with breast cancer. Instead, it appears that DNA hypermethylation leads to aberrant regulation of the Wnt pathway in breast cancer, and as such, this review focuses on the epigenetic regulation of Wnt pathway components in breast cancer.